US Import Duty Calculator: What to Enter Before You Quote

An import duty calculator is a multiplication engine: it takes a duty rate and applies it to a customs value. The rate comes from the HTS code and origin combination; the value comes from the commercial invoice, incoterm, and freight/insurance terms. If either input is wrong or approximate, the output — however precisely it is calculated — is only a rough screen rather than a quote-grade estimate.

For planning purposes, a rough screen is better than no estimate at all. Many sourcing and pricing decisions start with a single question: is this product likely to face high, medium, or low duty exposure? A quick keyword lookup and a broad rate assumption can answer that directional question. But before a quote goes to a customer or a purchase order is issued, the estimate should be rebuilt with the confirmed HTS code, the verified origin, and the actual commercial terms.

The two most common sources of error in import duty estimates are (1) using a six-digit HS code or product keyword instead of the specific 10-digit US HTS subheading, and (2) using the supplier's country as a proxy for origin when the actual manufacturing country may be different. Both errors can produce estimates that are off by several percentage points, which on a $100,000 shipment translates to thousands of dollars of variance between the estimate and the actual duty bill.

Use the most specific HTS code available, not only a product keyword. The US Harmonized Tariff Schedule is organized at the 10-digit level for import purposes, and duty rates are determined at that level. A broad heading can hide significant duty differences at the subheading level — for example, different subheadings within the same 4-digit heading can carry duty rates ranging from duty-free to more than 20 percent, depending on material, construction, or end-use.

To find the right HTS subheading, start with the product's primary material and principal function. For physical goods, the tariff schedule's general rules of interpretation and the chapter-level notes define which classification principles take precedence when a product could fall under multiple headings. Products with multiple components are generally classified by their essential character. Products explicitly listed in the schedule take precedence over general descriptions.

Once you have a candidate HTS code, check the current duty rate in the USITC online tariff viewer. Confirm the rate column that applies to your origin country — Column 1 General for MFN countries, Column 2 for the very small number of non-NTR countries, and the Special column for goods qualifying under a free trade agreement. Save the code and the rate source date so the record is auditable if the rate changes before the shipment arrives.

Country of origin and country of shipment are different, and confusing them is one of the most common causes of duty estimate errors. The country of origin is the country where the goods were substantially manufactured or transformed. The ship-from country is where the goods were last loaded. A product assembled in Vietnam from Chinese-made components may ship from Vietnam but still be classified as China-origin under US rules if substantial transformation occurred in China.

Origin determines whether Section 301 duties, antidumping orders, countervailing duty orders, or other trade actions apply. Origin also determines which FTA preferential rates the importer can claim. Getting origin wrong in the estimate can make a duty-free product look dutiable, or make a heavily tariffed product look cheaper than it will actually be at entry.

For goods with complex supply chains — electronics, apparel, furniture, and many consumer goods — origin determination may require a detailed manufacturing analysis under US rules of origin. The substantial transformation test asks whether the processing done in a country changes the tariff classification (a tariff-shift), adds sufficient value, or meets a specific manufacturing test. If there is genuine uncertainty about origin, a broker review or a CBP ruling request is more appropriate than a directional estimate.

US customs duty is assessed on the transaction value of the goods, which is generally the price paid or payable for the goods when sold for export to the United States. This is typically the commercial invoice value. Freight and insurance costs are not included in the US customs value if the goods are valued on a free on board (FOB) origin basis — but are included if the commercial terms include them in the invoice price (such as CIF or DDP terms).

MPF and HMF are also calculated from the entered value. MPF is calculated from the commercial value regardless of the freight term; HMF is calculated from the value of cargo. Understanding which value basis applies is important because it affects the duty calculation directly. For a CIF shipment, the customs value includes freight and insurance — which means the duty base is larger than the product cost alone.

Enter customs value, freight, and insurance consistently with the quote terms so landed-cost totals can be compared later. If your quote is on an FOB basis, enter the FOB value as the customs value and the actual freight and insurance separately. If your quote is CIF, the CIF value is the customs value, and you should note that freight and insurance are already embedded in the duty base. Inconsistent treatment is one of the most common reasons two landed-cost models for the same shipment produce different numbers.

Treat the estimate as a planning record, not a CBP determination. The calculator produces a model output based on the inputs you provide. CBP determines the actual duty owed at the time of entry based on the entry documents, the entered value, and the classification the importer (through their broker) declares. A planning estimate and a CBP entry determination can differ because of classification changes, value adjustments, or trade-action modifications between the time of the estimate and the time of entry.

Save the HTS code, origin assumption, commercial terms, freight amount, insurance amount, duty-rate source, and calculation date with the quote. When either the product changes (a new supplier, a modified specification) or the trade environment changes (a new tariff action, an exclusion expiry), you can quickly identify which quotes are affected and re-run the calculation with the updated inputs rather than rebuilding from scratch.

For regulated products, high-value shipments, or goods with material trade-action exposure, route the estimate to a broker review before committing pricing to the customer. A licensed customs broker who reviews the entry at the time of shipment is a different function from a tool used at the time of quote planning — both are part of a professional import compliance process, and neither substitutes for the other.